The star has light variability arising from varying concentrations of various chemical elements across its surface and it has a rotation period of 5.1 days, the same as the claimed orbital period of the substellar companion. I therefore have to wonder whether the radial velocity variations might be arising due to processes intrinsic to the star, something which was only briefly addressed in Sokolov's paper.

Here some cases of substellar objects with mass around or below the 25 Jupiter masses thresold established for the Extrasolar Planet Encyclopaedia. I hope these ones may be listed in the planet counter of EPE soon:

I also have got the paper of Kraus & Hillenbrand (2007) with a full table of young stars with widely separated stellar and substellar companions. Oddly the same full table is not viewable in current fulltext of this paper. I don't know if there has been an embargo risk and original draft withdrawn.

Adopting the upper limits for P and K, the companion would have to be a brown dwarfwith ≃ 20MJ and a radius of ≃ 0.1R⊙. For inclinations lower than 90◦ the orbital periodof the putative binary must be shorter, because the absolute rotational velocity of the sdBhas to be higher to keep vrot sin i fixed at the observed value.

From slightly later in the EC 2210-1916 paper from where you quoted...

These simple calculations show that the possible parameter space of a close and synchronised binary would be extremely narrow (P ≃ 0.1−0.15 d, K ≃ 4−12 km s−1). Furthermore, all possible conﬁgurations would lead to photometric variabilities easily visible in the light curve. Close sdB+dM or BD systems are not only often eclipsing, but also show sinusoidal variations due to light from the irradiated surface of the cool companion (e.g. ěstensen et al. 2010; For et al. 2010; Geier et al. 2011a). Due to its high temperature and low surface gravity EC 22018−1916 has a very high luminosity compared to other sdBs, which should lead to a very strong reﬂection effect at inclinations of ≃ 50░ or higher. Since no variations were found in the ASAS and NSVS light curves (Figure 4), a nearby low-mass companion can be excluded as well.

A complex two-month-long eclipse observed for the star 1SWASP J140747.93-394542.6 may have been due to a disk surrounding an otherwise-unknown planet, though it is also possible that the occulting disk instead adorns a low-mass stellar companion (Mamajek et al. 2011).